1. Field of the Invention
The present invention relates to a liquid crystal display, and more particularly, to a liquid crystal display structure with a simplified fabrication process, and a fabrication method thereof.
2. Discussion of the Related Art
Generally, a liquid crystal display (LCD) displays an image corresponding to data signals on an LCD panel by controlling light transmittance of liquid crystal cells arranged in a matrix configuration on the LCD panel with video data signals supplied to each of the liquid crystal cells.
To achieve this, the LCD includes electrodes for applying an electric field to a liquid crystal layer, thin film transistors (TFTs) for selectively switching data supplied to the liquid crystal cells, data lines for supplying the liquid crystal cells with the data supplied from the exterior, and gate lines for supplying a control signal of the TFT.
The LCD is fabricated by various processes including a process of forming a lower substrate and an upper substrate of an LCD panel, accompanying a process for forming liquid crystal cells defining pixel units, a process of forming and rubbing an alignment film for aligning liquid crystal molecules, a process of attaching the upper substrate and the lower substrate, and a process of injecting and sealing liquid crystal between the upper plate and the lower plate. Here, a color filter, a common electrode and a black matrix are formed on the upper substrate. Signal lines such as data lines and gate lines are formed on the lower plate. Thin film transistor (TFT) is formed at a crossing portion of the data line and the gate line.
FIG. 1 is a plan view of a substrate of an LCD panel on which a plurality of thin film transistor arrays are formed.
Referring to FIG. 1, in the related art LCD fabrication method, a plurality of TFT arrays 13 are formed on a lower substrate 1. On the TFT array 13, gate lines 17 and data lines 15 are formed to cross each other at right angles. A thin film transistor (TFT) (not shown) and a pixel electrode (not shown) are formed at each crossing of the gate lines 17 and data lines 15. Each of the thin film transistor arrays 13 constitutes an independent display device.
Also, on the lower substrate 1, a pad part including a plurality of pads (not shown) connected with the data lines 15 and the gate lines 17 are provided. The pad part is connected with a shorting bar 12.
If the active layer of the thin film transistor provided on each pixel region of the LCD is made of polycrystalline silicon, a drive circuit can be formed by patterning polycrystalline silicon. Accordingly, a data drive circuit (not shown) connected with the data lines 15 of the thin film transistor array 13 and a gate drive circuit (not shown) connected with the gate lines 17 of the thin film transistor array 13 are mounted on the lower substrate 1. Also, the pad part (not shown) is connected with the gate drive circuit and the data drive circuit via corresponding link patterns. The shorting bar 12 is connected with the pad part. Here, the shorting bar 12 functions prevents static electricity from being generated while the fabrication processes are carried out.
Next, spacers are dispensed on the lower substrate 1, and seal pattern is formed on the upper substrate. The spacers and the seal pattern allow a gap to be formed between the upper substrate and the lower substrate. After that, the upper substrate 2 and the lower substrate 1 are attached to face each other, to form a mother LCD panel including a plurality of LCD panels. The mother LCD panel is then subjected to a scribing and/or breaking process and is thereby divided into a plurality of unit LCD panels.
After the scribing process is completed, liquid crystal is injected into the respective divided unit LCD panels through an injection hole in the seal pattern. The injection of the liquid crystal is carried out by the capillary phenomenon using a pressure difference between the inside of the LCD panel and the outside of the LCD panel. After the injection of the liquid crystal is completed, the injection holes are sealed and the divided unit LCD panels are subject to a grinding process in which the shorting bar is removed, and edges of the upper substrate and the lower substrate are ground to enhance a resistance against edge fracture that may be caused in the edges.
FIGS. 2A and 2B are plan views illustrating a periphery of a related art LCD. Specifically, FIG. 2A illustrates an amorphous silicon (a-Si) TFT LCD, and FIG. 2B illustrates a polycrystalline silicon (poly-Si) TFT LCD.
Referring to FIG. 2A, the related art LCD includes an upper substrate 2, a lower substrate 1 facing the upper substrate 2, a liquid crystal layer (not shown) interposed between the upper substrate 2 and the lower substrate 1, a plurality of pad parts 6 mounted on edges of the lower substrate 2, a plurality of data lines 15 and a plurality of gate lines 17 extending from respective pads 11 of the pad parts 6. The plurality of data lines 15 and the plurality of gate lines 17 are shaped in a matrix configuration. A pixel region (A) provided with thin film transistor and pixel electrode is formed at each of crossing portions of the plurality of data lines 15 and the plurality of gate lines 17.
The shorting bar 12 is provided above the pad parts 6 and is commonly connected with the pad parts 6. The shorting bar 12 is made of metal at edges of the lower substrate 1 corresponding to non-display region, and is removed from the lower substrate 1 while the edges of the lower substrate 1 are ground along cutting lines in the scribing process and the grinding process.
If the shorting bar 12 is removed as above, a tape carrier package (hereinafter referred to as ‘TCP’) is bonded on the pad parts by a drive circuit mounting method such as tape automated bonding (hereinafter referred to as ‘TAB’) method. In other words, output pads of the TCP are connected with the pad parts 6 on the lower substrate 1 and input pads of the TCP are connected with a printed circuit board (PCB).
Also, referring to FIG. 2B, the related art LCD includes an upper substrate 2, a lower substrate 1 facing the upper substrate 2, a liquid crystal layer (not shown) interposed between the upper substrate 2 and the lower substrate 1, a gate or data drive circuit 9 patterned on the lower substrate 1, for driving a plurality of data lines 15 or a plurality of gate lines 17, a plurality of pad parts 6 connected with the gate or data drive circuit 9 via a link pattern 4. The upper substrate 2 and the lower substrate 1 are attached to each other with a seal pattern 7 dispensed on edges of the upper substrate 2. Liquid crystal is injected into a space defined by attaching the upper substrate 2 and the lower substrate 1.
The gate or data drive circuit 9 is located within the seal pattern 7 within a region defined by attaching the upper substrate 2 and the lower substrate 1 and is connected with the data lines 15 or the gate lines 17. A pixel region (A) including thin film transistor and pixel electrode is formed at each of crossing portions of the data lines 15 and the gate lines 17.
Also, a shorting bar 12 is provided outside the pad parts 6 and is commonly connected with the pad parts 6. The shorting bar 12 is grounded to a GND terminal during the LCD fabrication process and functions to eliminate static electricity applied to the LCD panel. The shorting bar 12 is formed for the purpose of performing IPT (In Processing Test) for the plurality of pad parts 6.
The shorting bar 12 is made of metal at edges of the lower substrate 1 corresponding to non-display region and is removed from the lower substrate 1 while the edges of the lower substrate 1 are ground along cutting lines in the scribing process and the grinding process.
FIGS. 2A and 2B are discriminated from each other by a difference in the material of the active layer, i.e., the active layer of FIG. 2A being made of amorphous silicon while the active layer of FIG. 2B being made of polycrystalline silicon. Hence, according to the material used as the active layer, the drive circuit may be patterned on the lower substrate or formed separately from the lower substrate.
As a result, the structures of the pad parts formed on the lower substrate and the shorting bar connected with the pad parts shown in FIG. 2A are the same as those shown in FIG. 2B. However, there is a difference between FIG. 2A and FIG. 2B in that in case of FIG. 2A, the data lines 15 and the gate lines 17 extend directly from the respective pads 11 of the pad parts 6, but in case of FIG. 2B, the data lines 15 and the gate lines 17 extend via the link pattern 4 formed by patterning within the pad part 6 and the drive circuit 9 from the respective pads 11 of the pad parts 6.
FIGS. 3A to 3C are plan views illustrating a state in which the shorting bar 12 shown in a selected portion of FIG. 2B is removed. It is noted that FIGS. 3A to 3C describe such a state with the example of FIG. 2B, but the shorting bar shown in FIG. 2A can be also removed by the same method.
A related art method for removing the shorting bar 12 will be described hereinafter with reference to FIGS. 3A to 3C.
First, as illustrated in FIG. 3A, during the scribing process, the respective unit LCD panels, i.e., thin film transistor arrays, are divided. At this point, a scribing wheel 16 scribes the mother LCD panel (the panel containing multiple unit LCD panels) along a cutting line 14 formed above the shorting bar 12.
In other words, by the scribing process, a portion of the shorting bar 12 is removed, and the remaining portion of the shorting bar 12 connected with the pad parts 6 is removed from the lower substrate 1 while it is ground by a grinding process using a grinding machine 18. The removal process of the shorting bar 12 is illustrated in FIG. 3B.
Thus, while the mother LCD panel is subject to the scribing process and the grinding process, the shorting bar 12 formed in the respective unit LCD panels is completely removed. The structure of the pad part when the shorting bar 12 is completely removed is illustrated in FIG. 3C.
However, if the shorting bar is removed as above, the shorting bar of metal may generate a lot of particles during the removal process, so that the pad may be damaged.
In addition, the scribing process and the grinding process essentially used for removing the shorting bar make the fabrication process of the LCDs complicated.